Proper ubiquitination effect on the fertilisation outcome post‐ICSI

Ubiquitin is an 8.5‐kDa protein that tags outlived proteins for degradation by the proteasome. It also marks defective spermatozoa during epididymal passage and has been proposed as a biomarker of sperm quality. This study evaluates the relationship between sperm ubiquitination, protamine deficiency, semen parameters and fertilisation rate in infertile individuals undergoing the intracytoplasmic sperm insemination (ICSI) procedure. Semen samples from 73 ICSI candidates were collected and analysed according to World Health Organization criteria. A portion of each sample was evaluated for sperm ubiquitination using the sperm ubiquitin tag immunoassay (SUTI) with flow cytometry, and protamine deficiency by chromomycin A3 (CMA3) staining. In addition, the relationship between the fertilisation rate and sperm ubiquitination was calculated in ICSI candidates. The intensity of ubiquitination showed a significant negative correlation with sperm concentration (r = ?0.255, P = 0.032) and a positive correlation with fertilisation rate (r = 0.384, P = 0.013) post‐ICSI. No correlation was observed between protamine deficiency and the percentage of ubiquitination or ubiquitination intensity. The results of this study suggest that sperm ubiquitination prior to capacitation may be considered as a marker of defective spermatozoon. Spermatozoa that undergo proper ubiquitination may have a higher chance for fertilisation, because they are made redundant by the ubiquitin–proteasome pathway in the epididymis compared to hypo‐ubiquitinated spermatozoa.     

Influence of extended incubation time on Human sperm chromatin condensation,sperm DNA strand breaks and their effect on fertilisation rate

The purpose of this study was to determine influence of extended incubation time on sperm chromatin condensation and DNA strand breaks and their effect on fertilisation rate. Forty couples undergoing ICSI therapy were included. Semen was prepared by PureSperm gradient centrifugation and divided into two parts. The first part (G1) was used immediately for ICSI, whereas the second part (G2) was kept in the incubator at 37°C, 5% and 90% Humidity for 5 hr, and thereafter, the capacitated spermatozoa were used for ICSI. The TUNEL test and chromomycin CMA3 were used to evaluate the DNA strand breaks and chromatin condensation respectively. The percentage of condensed chromatin was 73.92 ± 12.70 in the group 1 and 81.13 ± 10.31% in group 2 (p = .001). However, the double‐strand breaks were 11.15 ± 8.67% in G.1 and 16.30 ± 11.12% in G.2. (p = .001). Fertilisation rate in the (Group 1) was 62.45% and 69.17% in (Group 2). There was a positive correlation between condensed chromatin and fertilisation rate (r = 0.846, p = .001) and a negative correlation with DNA double‐strand breaks (r = ?0.802; p = .001). In conclusion, the prolonged sperm incubation (5 hr) leads to a higher chromatin condensation and to a significantly increased number of DNA strands double breaks with no influence on fertilisation rates.     

Pregnancy after intracytoplasmic sperm injection following extended sperm preparation and hormone therapy in an azoospermic man with maturation arrest and microlithiasis: a case report and literature review

In the management of azoospermia, a combination of testicular sperm extraction and intracytoplasmic sperm injection (ICSI) is usually the most successful option for fatherhood. However, an outstanding question remains: How can at least a few spermatozoa be obtained from the ejaculate, thus avoiding the need for a surgical procedure? A 36‐year‐old man presented to Assisted Reproduction Unit with his 26‐year‐old wife. The ultrasound assessment revealed bilateral microlithiasis. Two spermograms revealed absolute azoospermia. Levels of follicle‐stimulating hormone (FSH) and luteinising hormone were normal–low. The patient underwent 10 months of treatment with clomiphene citrate. A bilateral testicular sperm extraction failed to retrieve spermatozoa and revealed a maturation arrest at spermatocyte/spermatid stages depending on the tubules. Clomiphene citrate was replaced with recombinant FSH (rFSH). After 9‐month treatment with rFSH, motile spermatozoa from droplets of ejaculate pellet were cryopreserved as a single straw. Ovarian stimulation was provided using classic antagonist protocol, and five mature oocytes were collected. Two consecutive fresh semen samples on the day of ICSI yielded seven motile spermatozoa, and fertilisation was achieved in all five oocytes. On day 3, two embryos were transferred, yielding positive beta‐human chorionic gonadotropin and a healthy delivery of a boy and a girl.     

Correlation analysis of the progesterone‐induced sperm acrosome reaction rate and the fertilisation rate in vitro

In this study, we aimed to investigate whether progesterone‐induced acrosome reaction (AR) rate could be an indicator for fertilisation rate in vitro. Twenty‐six couples with unexplained infertility and undergoing in vitro fertilisation (IVF) treatment were involved. On the oocytes retrieval day after routine IVF, residual sperm samples were collected to receive progesterone induction (progesterone group) or not (control group). AR rate was calculated and fertilisation rate was recorded. The correlation between progesterone‐induced AR and fertilisation rate and between sperm normal morphology and 3PN (tripronuclear) were analysed using the Spearman correlation analysis. The AR rate of progesterone group was statistically higher than that of the control group (15.6 ± 5.88% versus 9.66 ± 5.771%, P < 0.05), but not significantly correlated with fertilisation rate (r = ?0.053, P > 0.01) or rate of high‐quality embryo development (r = ?0.055, P > 0.01). Normal sperm morphology also showed no significant correlation with the amount of 3PN zygotes (r = 0.029, P > 0.01), rate of 3PN zygotes production (r = 0.20, P > 0.01), rate of 3PN embryo development (r = ?0.406, P > 0.01), fertilisation rate (r = ?0.148, P > 0.01) or progesterone‐induced AR rate (r = 0.214, P > 0.01). Progesterone can induce AR in vitro significantly; however, the progesterone‐induced AR may not be used to indicate fertilisation rate.     

Investigation of the association between the outcomes of sperm chromatin condensation and decondensation tests,and assisted reproduction techniques

The main purpose of this prospective study is to examine possible influences of abnormalities of sperm nuclear condensation and chromatin decondensation with sodium dodecyl sulphate (SDS)‐EDTA on outcomes of intrauterine insemination (IUI) or intracytoplasmic sperm injection (ICSI) cycles. Semen samples from 122 IUI and 236 ICSI cycles were evaluated. Before semen preparation for IUI or ICSI, basic semen analysis was performed and a small portion from each sample was spared for fixation. The condensation of sperm nuclear chromatin was evaluated with acidic aniline blue, followed by sperm chromatin decondensation by SDS‐EDTA and evaluation under light microscope. Ongoing pregnancy rate was 24% and 26.2% in the IUI and ICSI groups respectively. The chromatin condensation rate was significantly higher in the ongoing pregnancy‐positive group compared to the negative group, both in IUI (P = 0.042) and ICSI groups (P = 0.027), and it was positively correlated with ongoing pregnancy rate in both IUI and ICSI groups (P = 0.015, r = 0.214 and P = 0.014, r = 0.312 respectively). Chromatin decondensation rates were not significantly different in neither of the groups. These results indicate that IUI and ICSI outcome is influenced by the rate of spermatozoa with abnormal chromatin condensation. Sperm chromatin condensation with aniline blue is useful for selecting assisted reproduction techniques (ART) patients.     

Relationship between hyaluronic acid binding assay and outcome in ART: a pilot study

The sperm–hyaluronan binding assay (HBA) is a diagnostic kit for assessing sperm maturity, function and fertility. The aim of this prospective cohort pilot study was to evaluate the relationship between HBA and WHO sperm parameters (motility, concentration and detailed morphology) and possible influence of sperm processing on hyaluronic acid binding. A cohort of 68 patients undergoing a first combo in vitro fertilisation/intracytoplasmic sperm injection treatment after failure of three or more intrauterine insemination cycles were included in the study. Outcome measures studied were fertilisation rate, embryo quality, ongoing pregnancy rate and cumulative pregnancy rate. HBA outcome improved after sperm preparation and culture, but was not correlated to detailed sperm morphology, concentration or motility. HBA did not provide additional information for identifying patients with poor or absent fertilisation, although the latter had more immature sperm cells and cells with cytoplasmic retention present in their semen. HBA outcome in the neat sample was significantly correlated with embryo quality, with miscarriage rates and ongoing pregnancy rates in the fresh cycles, but not with the cumulative ongoing pregnancy rate. No threshold value for HBA and outcome in combo IVF/ICSI treatment could be established. The clinical value for HBA in addition to routine semen analysis for this patient population seems limited.     

Patients with multiple morphological abnormalities of the sperm flagella harbouring CFAP44 or CFAP43 mutations have a good pregnancy outcome following intracytoplasmic sperm injection

Multiple morphological abnormalities of the sperm flagella (MMAF) are a rare type of male infertility. Mutations in DNAH1, CFAP43 and CFAP44 are the main aetiology of the disorder. Previously, good intracytoplasmic sperm injection (ICSI) outcomes were reported for MMAF patients with DNAH1 mutations. However, the ICSI prognosis for MMAF patients with CFAP43 or CFAP44 mutations was not known. We designed a retrospective cohort study. Molecular genetic testing identified six MMAF patients with biallelic CFAP44 (CFAP44⁺ group) or CFAP43 mutations and 12 patients with homozygous or compound heterozygous DNAH1 mutations (DNAH1⁺ group). A control group consisted of age‐matched, non‐MMAF men. For MMAF patients carrying CFAP44 mutations, the recorded rates of fertilisation, transferable embryos, pregnancy and delivery after ICSI were 76.47%, 88.46%, 50.0% and 50.0% respectively. The fertilisation rate was significantly higher in the CFAP44⁺ group than in the DNAH1⁺ group (76.47% vs. 54.5%, p = 0.0196). There were no statistically significant differences in the rates of transferable embryos, implantation, clinical pregnancy and miscarriage between the CFAP44⁺ group and either the DNAH1⁺ group or the age‐matched control group. Our results support a good ICSI prognosis for MMAF patients carrying CFAP44 or CFAP43 mutations.     

Impact of using a fast‐freezing technique and different thawing protocols on viability and fertility of frozen equine spermatozoa

The effects of freezing technique and thawing protocol on thawed semen viability and fertility were studied. Ejaculates from 5 stallions (n = 25) were frozen by conventional or a fast‐freezing technique. Frozen semen was thawed by two thawing protocols (37 °C 30 s^?1 or 75 °C 7 s^?1). Thawed semen was evaluated by progressive motility, vigour, morphology and plasma membrane integrity. Mares (n = 25) were inseminated with 300 (n = 11) or 150 (n = 14) million spermatozoa. A greater (P < 0.05) vigour and progressively motile spermatozoa were detected, respectively, at thawing and after 20 min post‐thawing in the fast‐freezing technique than in the conventional one. Plasma membrane integrity was also greater (P < 0.05) in semen frozen with the fast‐freezing technique. Semen viability was not affected by thawing protocol. Pregnancy rate using the fast‐freezing technique was 76% (19/25), and did not differ (P > 0.05) between insemination doses. We concluded that the 150 million progressively motile spermatozoa per dose using a deep‐horn insemination maximises the use of equine semen. The fast‐freezing technique, as compared to the conventional one, efficiently preserves the viability and fertilising capacity of spermatozoa, indicating a new method to improve the fertility of frozen equine semen.     

Spermatozoa retrieved by electroejaculation: Should we prefer fresh or cryopreserved spermatozoa for intracytoplasmic sperm injection?

We aim to evaluate our experience, comparing intracytoplasmic sperm injection (ICSI) outcomes of cycle using fresh versus thawed electroejaculated spermatozoa. All consecutive couples undergoing ICSI cycles using electroejaculated spermatozoa, during a 16-year period, were evaluated. Embryological/laboratory variables of the ICSI cycles were assessed and compared between those utilising fresh (fresh group) versus thawed (thawed group) electroejaculated spermatozoa. Fifty-seven couples were evaluated, 30 used a fresh electroejaculated spermatozoa in 55 ICSI cycles, while 27 used a thawed sperm sample in 41 ICSI cycles. There were no in-between group differences in the mean numbers of oocytes retrieved per oocyte retrieval nor the percentage of MII oocytes. The fresh group demonstrated significantly higher fertilisation (71.5% vs. 64.1%, respectively, p < .05), top-quality embryos (66.5% vs. 54.9%, respectively, p < .02), clinical pregnancy per transfer (41.3% and 21.2%, respectively, p < .05) and cumulative clinical pregnancy (58.2% vs. 26.8%, respectively, p < .001) rates, as compared to the thawed group. Independent of the source of spermatozoa used, no pregnancy was achieved following ICSI utilising immotile spermatozoa. In conclusion, ICSI cycles using ejaculated spermatozoa of patients suffering from neurologic or psychogenic anejaculation are reassuring. The use of fresh ejaculated spermatozoa retrieved on the day of the female spouse oocyte retrieval might improve outcome. Whenever a thawed electroejaculated spermatozoa yield no motile spermatozoa, emergency electroejaculation is mandatory.     

Apoptotic sperm biomarkers and the correlation between conventional sperm parameters and clinical characteristics

The principal aim of this retrospective study was to examine the relationship between sperm apoptotic biomarkers and the patient's biclinical characteristics, the conventional sperm parameters and the results of assisted reproductive technology. Sperm analysis, activated caspases, annexin V staining for phosphatidylserine (PS) externalisation and labelling assay for DNA fragmentation were assessed in 122 males of infertile couples. Fifty‐seven couples were allocated to the natural conception group, and 65 couples underwent IVF or ICSI. Semen of IVF/ICSI patients showed a higher proportion of apoptotic spermatozoa in their spermatozoa when compared with a natural conception group (p < .05). Sperm apoptotic biomarkers correlated with age, FSH, and conventional sperm parameters. DNA fragmentation correlated positively with the percentage of semen having externalised PS (r = .78, p = 0) and activated caspases (r = .71, p = 0). Patients without clinical pregnancy had higher frequency of DNA fragmentation, externalised PS and activated caspases compared to patients with clinical pregnancy (p < .001). The best specificity and greater sensitivity were obtained with the test of the DNA fragmentation compared to the other biomarkers. Among the apoptotic biomarkers, only DNA fragmentation was found to predict natural or assisted pregnancy better than conventional sperm parameters.     

Testicular spermatozoon is superior to ejaculated spermatozoon for intracytoplasmic sperm injection to achieve pregnancy in infertile males with high sperm DNA damage

The purpose of this study was to compare the clinical outcome of testicular spermatozoon versus ejaculated spermatozoon in the treatment of infertile males with high sperm DNA damage, referred as sperm DNA fragmentation index (DFI), that attending intracytoplasmic sperm injection (ICSI) programme in terms of clinical pregnancy, births delivered as the primary and pregnancy loss and embryo fertilisation as the secondary outcome. A total of 102 males fulfilling the inclusion criteria were enrolled in the present study. Of the 102 males, 61 infertile males underwent testicular spermatozoon combined with ICSI while the remaining 41 males applied ejaculated spermatozoa in their first ICSI cycles, and the data of them were collected and analysed. In a 18‐month follow‐up, testicular spermatozoon achieved higher pregnancy rate and deliver rate than those in ejaculated sperm group (pregnancy rate, 36% vs. 14.6%, p = 0.017; deliver rate, 38.5% vs. 9.8%, p = 0.001). Nevertheless, there were no significant differences in the number of oocytes aspirated and number of embryos transferred between the two groups. Additionally, the fertilisation rate in the testicular sperm study cohort (70.4%) was also similar to that in the ejaculated sperm group (75.0%). Based on the current data, we conclude that testicular spermatozoon is the prior option in the treatment of infertile males with high sperm DFI in ICSI programme. More high‐quality studies with larger samples size are needed in the future due to the relative small size and the nonrandomized design of the present study.     

Assessment of sperm hyperactivated motility and acrosome reaction can discriminate the use of spermatozoa for conventional in vitro fertilisation or intracytoplasmic sperm injection: Preliminary results

Basic semen analysis is insufficient for determining the fertility potential. The aim of this study was to determine if hyperactivated motility (HAM) and acrosome reaction (AR) can be useful tests for evaluating semen quality during male infertility evaluations and to help the clinician decide whether regular insemination or intracytoplasmic sperm injection (ICSI) is preferable during in vitro fertilisation. A prospective study was conducted. Patients with normal sperm according to World Health Organization guidelines who underwent IVF treatment and planned regular insemination were asked to participate. A portion of sperm sample was evaluated for HAM and AR on day of ovum pick up. In HAM assessment, 93.3% of patients with increased HAM had a high fertilisation rate compared with 64% in the group without increased HAM (P = 0.059). For the AR evaluation, 91.7% of samples with a low rate of spontaneous AR had a high fertilisation rate compared with 39.3% in the group with a high rate of spontaneous AR (P = 0.004).     

Frequency of sex chromosomal disomy in spermatozoa of normal and oligozoospermic Iranian patients and its effects on fertilisation and implantation rates after ICSI

Chromosomal aneuploidy is a well‐known phenomenon in human gametes including spermatozoa. Success rate of fertilisation and implantation in subfertile patients with male factor has always been shown to be very low. We tried to relate the possible impact of sex chromosomal aneuploidy in spermatozoa used for intracytoplasmic sperm injection (ICSI) on fertilisation and implantation rate. To evaluate the frequency of disomy for X and Y chromosomes in sperm samples retrieved from normal and oligozoospermic individuals, primed in situ labelling (PRINS) technique was used. Following ICSI, the rate of eight‐cell embryos for each category was determined and followed up for successful implantation. Results showed a statistically significant higher frequency of disomy for all chromosomes under study in spermatozoa of oligozoospermic patients compared with normal men (P < 0.01). The rate of eight‐cells embryo formation was significantly lower than in normal group (P < 0.01). The number of embryos transferred for both groups were nearly similar. Implantation rate for oligozoospermic patients was much lower than that of the normal group but was not significantly different (P > 0.05). These results demonstrate that men especially with severe oligozoospermia have an elevated risk for chromosome abnormalities in their spermatozoa. These abnormalities might affect fertilisation and pre‐embryo formation with less impact on implantation.     

In vitro equine embryo production using air‐dried spermatozoa,with different activation protocols and culture systems

The aim of this work was to evaluate the use of air‐dried spermatozoa for in vitro production of equine embryos and verify if sperm extract activation and in vivo culture improve in vitro embryo production. Cooled spermatozoa (control) and air‐dried spermatozoa stored for 2, 14 or 28 days were used for ICSI sperm extract, or ionomycin was used for oocyte activation, and embryos were in vitro or in vivo (in mare′s oviduct) cultured for 7 days. With in vitro culture, cleavage rate was higher when activating with sperm extract (P < 0.05). No differences in embryo development were seen between the two activation treatments nor between storage periods (P > 0.05). Blastocysts were obtained with cooled spermatozoa, and morulae were achieved using in vivo culture with 28‐day storage spermatozoa and ionomycin‐activated oocytes. When in vivo culture was performed, sperm DNA fragmentation was assessed using the sperm chromatin dispersion test and did not show statistical correlation with cleavage nor embryo recovery rates. In conclusion, equine embryos can be produced using air‐dried spermatozoa stored for several weeks. Sperm extract activation increased cleavage rates but did not improve embryo development. In vivo culture allowed intrauterine stage embryos to be achieved.     

Comparison of conventional in vitro fertilisation and intracytoplasmic sperm injection outcomes in patients with moderate oligoasthenozoospermia

The method of choice for assisted reproductive technology treatment in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) is usually based on the evaluation of male infertility factors. Decisions for couples with moderate oligoasthenozoospermia (OA) are often empirical because uniform treatment criteria are lacking. This study aimed to evaluate the effect of patients with moderate OA treated with conventional IVF and ICSI. A total of 199 couples with moderate OA undergoing their first IVF/ICSI cycle were included in the study. The patients were divided into two groups according to the type of insemination: conventional IVF group (n = 97) and ICSI group (n = 102). All patients were randomised to be inseminated either by conventional IVF or ICSI. The fertilisation rate, embryo quality, implantation rate and clinical pregnancy rate were examined. No differences in the fertilisation, implantation and pregnancy rates were observed between conventional IVF and ICSI groups (P > 0.05). However, the number of good‐quality embryos was significantly higher in the ICSI group than in the IVF group (P < 0.05). Couples with moderate OA did not influence on the overall clinical outcomes between IVF and ICSI treatments, and a negative influence by ICSI on blastocyst development was not confirmed.     

The influence of testicular microlithiasis on the outcomes of in vitro fertilisation in a Chinese Han population

To investigate the influence of testicular microlithiasis (TM) on the outcomes of in vitro fertilisation (IVF), we retrospectively reviewed the ultrasonography results of the TM patients who underwent IVF treatment in our hospital. They were classified as classic‐TM (CTM) or limited‐TM (LTM) comparing with patients without TM (Non‐TM). Semen parameters, rates of fertilisation, normal fertilisation, good embryos and clinical pregnancy were analysed. The Non‐TM group showed higher percentage of morphologically normal spermatozoa than the CTM or LTM group (4.08 ± 2.07 versus 3.40 ± 2.00 versus 3.04 ± 1.66, p = .003) while the other general semen parameters were comparable. The LTM group showed higher rate of fertilisation than the CTM group (85.10% versus 81.12%, p = .044). Moreover, the rates of normal fertilisation of Non‐TM (62.47%) and LTM (66.32%) group were significantly higher than the CTM (58.02%) group (p = .027 and p = .001 respectively). There were 333 embryo transfer cycles in total (including 222 fresh and 111 frozen). The overall clinical pregnancy rate was 54.95%, 58.33% and 64.12% in the group of CTM, LTM and Non‐TM respectively. However, no statistically significant difference was obtained (p = .326). Our results suggest that TM may have influence on the IVF outcomes. The extent of microlithiasis correlates inversely with the rates of fertilisation and normal fertilisation.     

Effect of brain‐derived neurotrophic factor on sperm function,oxidative stress and membrane integrity in human

Oxidative stress has negative impacts on the clinical outcomes of assisted reproduction techniques. The brain‐derived neurotrophic factor (BDNF) promotes the viability of nerve cells and is known to decrease oxidative stress and apoptosis in different cells. The aim of this study was to evaluate the effect of BDNF treatment on human sperm functions that are known to be essential for fertilisation. Our findings showed that treatment of human spermatozoa with 0.133 nM BDNF significantly increased the percentages of both total (P = 0.001) and progressive (P < 0.01) motile sperm cells compared to those observed in the nontreated (control) group. We also showed that the mean fluorescence intensity of DCFH‐DA, as an indicator of intracellular reactive oxygen species, was significantly lower (P < 0.05) in spermatozoa treated with BDNF compared to the control group. Treatment of spermatozoa with BDNF significantly decreased the percentages of both dead (P = 0.001) and apoptotic‐like sperm cells (P < 0.05) compared to the control group. On the other hand, BDNF treatment significantly increased the percentage of viable sperm cells compared to the control (P = 0.001). In conclusion, BDNF has protective effects against oxidative stress in spermatozoa and could improve sperm functions that are essential for sperm–egg fusion and subsequent fertilisation.     

Different outcomes after intracytoplasmic sperm injection without oocyte activation in two patients with different types of globozoospermia

Different outcomes after intracytoplasmic sperm injection (ICSI) without oocyte activation in two patients with different types of round‐headed spermatozoa (globozoospermia) are reported. After controlled ovarian hyperstimulation and oocyte pick‐up, retrieved oocytes were underwent ICSI without oocyte activation and a 33.33% (4/12) fertilisation rate was obtained in the first case, whereas an abnormal fertilisation was achieved in the second case. The transfer of two grade II embryos in the first couple resulted in clinical pregnancy with a healthy livebirth. It was concluded that the main problem of cases with globozoospermia was a low fertilisation rate or failure fertilisation, and even though ICSI and artificial oocyte activation have been employed to increase this rate, it is not necessarily needed to achieve a pregnancy.     

Sperm source does not affect the ICSI outcome of patients with severely compromised spermatogenesis

Patients with spermatogenic dysfunction may display sperm parameters ranging from extremely severe oligozoospermia (sperm count lower than 2 million/ml) to azoospermia. It has been proposed that, since these patients may have increased sperm DNA damage that could affect their ICSI outcome, the use of surgically retrieved testicular spermatozoa should be preferred to improve their chance of fathering their biological offspring. However, studies in this field have yielded conflicting results. The present study provides an updated assessment of this subject by comparing the ICSI outcome of 762 patients with nonobstructive azoospermia and 419 with sperm count lower than 2 million/ml (median sperm count 300,000/ml). Both groups were homogeneous for the number of retrieved and injected MII oocytes. No difference was seen in terms of fertilisation, clinical pregnancy and cumulative live birth rates. Only the number of injected MII oocytes was found to independently predict the live birth rate, even when adjusted for the number of transferred embryos (OR 1.10 (1.0–1.2, p = 0.038)). The results of the present study stand against the use of testicular spermatozoa in patients with extremely severe spermatogenic dysfunction with available spermatozoa in their ejaculate.     

Utilisation of sperm‐binding assay combined with computer‐assisted sperm analysis to evaluate frozen‐thawed bull semen

Due to homologies between the chicken egg perivitelline membrane with mammalian zona pellucida proteins, spermatozoa of several species are able to bind to this membrane. However, adequate standardisation is required to attest possible applications of this technique for semen evaluation of a given species. Therefore, we thawed and divided cryopreserved semen samples into two aliquotes, one kept in water bath at 37 °C (thawed) and the other submitted to snap‐freezing to damage sperm cells (dead spermatozoa). Aliquotes were mixed into different ratios of thawed:dead cells and analysed for motility, membrane and acrosomal integrity, and mitochondrial activity. In parallel, chicken egg perivitelline membranes were inseminated with these ratios, and the number of spermatozoa bound per mm² of membrane was assessed by conventional microscopy (CM) and computer‐assisted sperm analysis (CASA). Linear regression showed high correlation between thawed:dead sperm ratio and number of spermatozoa bound to the membrane (CM: r² = 0.91 and CASA: r² = 0.92 respectively). Additionally, positive correlations were found between the number of spermatozoa bound to the membrane and acrosomal integrity, membrane integrity, mitochondrial activity and motility. These findings indicate that sperm‐egg‐binding assay associated with CASA is a reliable, practical and inexpensive method for examining the fertilising capacity of cryopreserved bull semen.